This invention is directed to metallocene catalyst systems for olefin polymerization. More particularly, the invention is directed to a method for temporarily and reversibly passivating metallocene catalysts to provide metallocene compositions useful as latent olefin polymerization catalysts.
The latent olefin polymerization catalysts of this invention, when activated, are particularly useful in the polymerization of alkenes, including 1-olefins such as propylene, in a gas-phase reactor.
The process technology for the manufacture of polypropylene (PP) has evolved with improvement in catalyst technology, from complex slurry processes using an inert hydrocarbon diluent, to simpler bulk processes using liquid propylene diluent, to even more simplified gas phase processes.
Gas phase reactor processes widely known and well described in the art include those based on continuously stirred tank reactor and fluid bed technologies. Examples of such reactor systems are described in U.S. Pat. Nos. 3,957,448; 3,965,083; 3,971,786; 3,970,611; 4,129,701; 4,101,289; 3,652,527; and 4,003,712, all incorporated herein by reference. Typical gas-phase olefin polymerization reactor systems comprise at least one reactor vessel to which olefin monomer and catalyst components can be added and which contain an agitated bed of forming polymer particles. Generally, catalyst components are added together or separately through one or more valve-controlled ports in the single or first reactor vessel. Olefin monomer may be provided to the reactor through a recycle gas system in which unreacted monomer removed as off-gas and fresh feed monomer are mixed and injected into the reactor vessel. Polymerization will be carried out under conditions that exclude oxygen, water, and other materials that act as catalyst poisons. Polymer molecular weights are controlled through use of additives such as hydrogen in a manner well known to persons of skill in the art.
The Amoco Gas Phase Process may be generally characterized as being conducted using two horizontal, stirred-bed, gas phase reactors in series. The plug-flow reactors employ an interlock system separating the first stage homopolymer reactor from the second stage copolymer reactor. The process provides an inherently narrow residence time distribution coupled with optimized stirring, minimizing temperature variations and resulting in greater product consistency. The Amoco process is disclosed generally in xe2x80x9cPolypropylene Handbookxe2x80x9d pp. 297-298, Hanser Publications, N.Y. (1996), and is more fully described in U.S. Pat. No. 3,957,448 and in xe2x80x9cSimplified Gas-Phase Polypropylene Process Technologyxe2x80x9d presented in Petrochemical Review March, 1993. The teachings of these publications and the patent are hereby incorporated in their entirety by reference.
Rubber-modified polypropylene resins are prepared commercially for the most part by post-blending separately produced homopolymer and copolymer resins in a compounding operation. In-reactor processes wherein homopolymer formed from the first monomer in a first reactor is subsequently reacted with the second monomer in a second reactor have also been disclosed and described in the art. Gas phase reactor processes such as are described in Hydrocarbon Processing 74 pp. 140-142 are disclosed to be useful for the production of impact PP resins. The two-stage horizontal gas phase reactor described in Polyolefins VI SPE RETEC, Houston, Tex. (1991), page 68 has also been employed in the production of impact polypropylene. Processes for use in the manufacture of copolyolefins have been further described in Petrochemical Review, March, 1993, in U.S. Pat. No. 3,957,448 and in Chemical Engineering Science Vol. 47, no. 9-11 (1992) pp. 2591-2596.
The polymerization catalysts conventionally employed in these processes have generally been Ziegler-Natta type catalysts. For example, the Amoco gas phase process is disclosed in the art to employ fourth generation supported catalysts consisting of three components: a proprietary solid CD catalyst, a trialkylaluminum activator or cocatalyst, and an external modifier or donor. Separately, the catalyst components are inactive. Hence the CD catalyst and activator may be suspended in propylene and fed to the reactor as separate streams without initiating polymer formation in the feed lines.
Recently there has been developed a practical catalyst technology based on metallocene compounds, termed sixth generation catalysts by E. Albizzati et al. in xe2x80x9cPolypropylene Handbookxe2x80x9d. Metallocene catalysts, more particularly described as Group 4 or 5 metallocenes, are soluble organic complexes that result from the reaction of biscyclopentadienyl transition metal complexes (metallocenes) with a cocatalyst, generally an aluminum compound. Most metallocene catalysts employed for propylene polymerization are zirconium-based, and the most widely used cocatalyst is methylaluminoxane (MAO), derived from trimethylaluminum (TMA). Other metallocene catalyst systems disclosed in the art include combinations of metallocene dialkyls with boron compounds, further including trialkylaluminum compounds.
Supported metallocene-based catalyst systems, which may be more particularly described as fully active, metallocene-based catalyst systems immobilized on a particulate carrier having narrow size distribution such as a finely divided silica, alumina, MgCl2, zeolite or the like, are also known. Solution and bulk processes for ethylene and propylene polymerization employing supported metallocene-based catalysts have been disclosed and are well described in the art.
Metallocene catalysts are difficult to employ directly in conventional polymerization processes, and particularly in gas phase processes where the catalyst system will be dispersed in a hydrocarbon or in monomer and metered into the reactor through feed lines. Supported metallocene catalysts are optimally active when preactivated, i.e. combined with the cocatalyst component prior to being introduced into the reactor. Dispersing such catalysts in the olefin monomer stream for direct feed to the reactor system results in polymer formation and causes severe plugging of the feedlines. Moreover, polymerization proceeds before the catalyst system is dispersed fully and uniformly through the polymer bed in the reactor, resulting in highly active hot spots that promote the formation of lumps and plating out. The reactor rapidly becomes fouled, reducing catalyst yields and requiring frequent shutdowns to clean the reactor.
Inert gases, hydrocarbons and the like have been employed as diluents and as carriers for use with Ziegler-Natta catalysts. These methods have had some success when employed with soluble metallocene catalysts in solution and bulk polymerization systems. In gas phase processes employing continuously stirred tank reactor and fluid bed technologies, the use of such diluents and carriers for feeding supported metallocene catalyst systems to the reactor with the olefin stream has generally not been successful. Although the problem of plugging may be avoided by dispersing the supported catalyst in an inert hydrocarbon such as propane and separately metering the mixture to the reactor, it is difficult to adequately disperse the catalyst through the reactor polymer bed rapidly enough to avoid forming lumps and strings.
Temporarily reducing the activity of metallocene catalysts has been described in the art. For example, adding a dialkyborane or dialkylaluminum to the reactor during a polymerization to temporarily retard the activity of metallocene catalysts has been disclosed as a method for process control. However, catalyst activity is only partially retarded by such treatment. Catalysts directly treated with a dialkyborane or dialkylaluminum retain sufficient activity to initiate polymerization when dispersed in the monomer feed stream. Moreover, the recovery period is very brief, too brief to allow the catalyst system to be adequately dispersed in a stirred reactor gas phase reactor bed before the catalyst recovers and polymerization proceeds.
It is known that metallocene catalysts are deactivated by Lewis acids. Reactivating a Lewis acid-treated catalyst after it is dispersed in the reactor bed requires adding excess MAO, which is difficult to disperse because of its low volatility. Separately adding an alkali metal alkyl or alkaline earth metal alkyl and a fully active, supported metallocene catalyst to a reactor before contacting with monomer has been disclosed to be useful for avoiding lumps and wall formations in the suspension polymerization of ethylene polymers and copolymers. The use of Lewis bases to retard or terminate a metallocene catalyzed polymerization as a means for process control is also disclosed in the art. Restarting the polymerization, accomplished by adding excess MAO, may require adding as much MAO as was employed in the initial preparation of the catalyst. Due to poor volatility, dispersing the MAO uniformly through the reactor bed is difficult, and the polymerization activity after restart may be substantially reduced. Moreover, many Lewis base compounds are irreversible catalyst poisons. In a continuous process such poisons will accumulate in the reactor over time, requiring that the process be stopped while the reactor is cleaned.
Thus, there does not appear to be available a method for temporarily and reversibly passivating metallocene catalysts whereby catalyst activity becomes reduced to a level that will allow feeding the catalyst to the reactor in contact with olefin monomer and adequately dispersing the catalyst in the reactor polymer bed prior to reactivating.
This invention is directed to a method for temporarily and reversibly passivating metallocene catalysts wherein fully active metallocene catalysts may be temporarily and reversibly passivated by contacting with an effective amount of a passivating compound.
The temporarily and reversibly passivated metallocene catalysts of this invention, further characterized as latent olefin polymerization catalysts, will have substantially reduced activity for polymerization of olefins. The latent catalyst thus may be dispersed in an olefin monomer such as propylene, fed to the reactor and dispersed through the reactor polymer bed without polymerizing the monomer to a significant extent. Preferably, the latent catalyst will remain inactive as a polymerization catalyst for olefins under the intended operating conditions until suitably reactivated, for example, by being contacted with an effective amount of an activator in a subsequent reaction step.
The invention may be still further described and characterized as directed to a gas-phase polymerization process for the polymerization of olefins comprising reversibly passivating a conventional metallocene catalyst to provide a latent catalyst, feeding the latent catalyst to the reactor optionally in contact with monomer, then reactivating the catalyst and carrying out the polymerization.
The metallocene catalyst systems useful in the practice of this invention, also referred to in the art as metallocene catalysts and as metallocene catalyst complexes, comprise metallocenes selected from Groups 4 and 5 (IUPAC nomenclature) metallocenes and a suitable cocatalyst, preferably an aluminoxane cocatalyst such as methyl aluminoxane (MAO).
A great variety of metallocenes suitable for use in forming metallocene catalyst systems have been described in the art, including complexes of titanium, zirconium, hafnium, vanadium, niobium and tantalum. Illustrative of such complexes are:
dimethylsilyl-bis-(2-methyl-4;5-benzo[e]indenyl) zirconium dichloride; dimethylsilanediyl-bis-(3-tert-butyl-5-methylcyclopentadienyl) zirconium dichloride; diethylsilanediyl-bis-(3-tert-butyl-5-methylcyclopentadienyl) zirconium dichloride; methylethylsilanediyl-bis-(3-tert-butyl-5-methylcyclopentadienyl) zirconium dichloride; dimethylsilanediyl-bis-(3-tert-butyl-5-ethylcyclopentadienyl) zirconium dichloride; dimethylsilanediyl-bis-(3-tert-butyl-5-methylcyclopentadienyl)-dimethyl zirconium; dimethylsilanediyl-bis-(2-methylindenyl) zirconium dichloride; diethylsilanediyl-bis-(2-methylindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-ethylindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-isopropylindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-tert-butylindenyl)-zirconium dichloride; diethylsilanediyl-bis-(2-methylindenyl) zirconium dibromide; dimethylsulfide-bis-(2-methylindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-methyl-5-methylcyclopentadienyl) zirconium dichloride; dimethylsilanediyl-bis-(2-methyl-5-ethylcyclopentadienyl) zirconium dichloride; dimethylsilanediyl-bis-(2-ethyl-5-isopropylcyclopentadienyl) zirconium dichloride; dimethylsilanediyl-bis-(2-methylindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-methylbenzindenyl) zirconium dichloride; dimethylsilanediyl-bis-(2-methylindenyl) hafnium dichloride; dimethylsilyl-bis(2-methyl-4-phenylindenyl) zirconium dichloride; dimethylsilyl-bis(2-ethyl-4-phenylindenyl) zirconium dichloride; dimethylsilyl-bis(2-methyl-4-naphthylindenyl) zirconium dichloride; dimethylsilyl-bis-(2-ethyl-4-phenylindenyl) zirconium dichloride; dimethylsilyl-bis-(2-methyl-4-isopropylindenyl) zirconium dichloride; dimethylsilyl-bis-(2-ethyl-4-isopropylindenyl) zirconium dichloride; and isopropylidene(3-tert-butyl-cyclopentadienyl)(fluorenyl) zirconium dichloride.
Zirconium-based metallocenes have been found particularly useful in providing catalyst systems useful in the polymerization of propylene.
Metallocene catalyst systems further contain a cocatalyst. Particularly suitable are aluminoxane compounds, more particularly described as poly(hydrocarbyl aluminum oxide). Aluminoxanes are well known in the art and may be formed by reacting water with an alkylaluminum compound. Generally, in the preparation of aluminoxanes from, for example, trimethylaluminum and water, a mixture of linear and cyclic compounds is obtained.
The aluminoxanes may be prepared in a variety of ways. For example, an aluminum alkyl may be treated with water in the form of a moist solvent. Alternatively, an aluminum alkyl, for example trimethylaluminum, may be contacted with a hydrated salt such as hydrated ferrous sulfate, for example by treating a dilute solution of trimethylaluminum in toluene with a suspension of ferrous sulfate heptahydrate. It is also possible to form methylaluminoxanes by the reaction of a tetraalkyldialuminoxane containing C2 or higher alkyl groups with trimethylaluminum using an amount of trimethylaluminum which is less than a stoichiometric excess. The synthesis of methylaluminoxanes may also be achieved by the reaction of a trialkylaluminum compound or a tetraalkyldialuminoxane containing C2 or higher alkyl groups with water to form a polyalkylaluminoxane which is then reacted with trimethylaluminum. The synthesis of methylaluminoxanes, also known as modified aluminoxanes, by the reaction of a polyalkylaluminoxane containing C2 or higher alkyl groups with trimethylaluminum and then with water is disclosed in the art, for example, in U.S. Pat. No. 5,041,584. Suitable aluminoxanes may be obtained from commercial sources including Albemarle Corporation and Akzo-Nobel.
Suitable methods for combining the metallocene and cocatalyst to form the metallocene catalyst systems employed in the practice of this invention are well known and widely described in the art. The amount of aluminoxane and metallocene usefully employed in preparation of the catalytically active material can vary over a wide range. The mole ratio of aluminum atoms contained in the aluminoxane to metal atoms contained in the metallocene is generally in the range of from about 2:1 to about 100,000:1, preferably in the range of from about 10:1 to about 10,000:1, and more preferably in the range of from about 50:1 to about 2,000:1.
The reaction products of the metallocene and aluminoxane are generally solid materials that can be recovered by any well-known technique. For example, when produced in aliphatic solvents the solid material separates and can be recovered from the liquid by vacuum filtration or decantation; when produced in aromatic solvents the reaction products may be precipitated with a miscible non-solvent and then collected, or isolated by evaporating the solvent. The recovered catalytically active solid material may thereafter be dried under a stream of pure dry nitrogen or other inert gas, under vacuum, or by any other convenient manner.
The metallocene catalyst system may be employed directly for polymerization of olefins as a soluble catalyst, or may be supported on a suitable carrier such as, for example, finely divided silica, alumina, MgCl2, zeolite, layered clays, mesoporous molecular sieves or the like. Particulate polymeric substrates such as a finely divided polyolefin have also been employed for this purpose. The particulate carriers preferably will have a particle diameter in the range of from 1 to 300 microns, and more preferably from 20 to 70 microns. Carriers may be used directly or pretreated with MAO before depositing the metallocene component, and MAO/silica substrates have been disclosed in the art for use in providing metallocene propylene polymerization catalyst systems. Preparative methods for producing fully active, supported metallocene catalyst systems useful in the practice of this invention are described and disclosed in the art, including in EP 567,952 and EP 578,838, and in EP 810,233. A variety of substrates suitable for use in the practice of the invention including MAO/silica substrates are available from commercial sources such as, for example, Witco Corporation. Particularly useful silica substrates are available from Grace-Davison, PQ Corporation, Crosfield Chemicals, and Degussa Corporation.
Generally, the supported catalyst may be prepared by depositing the metallocene component on an MAO/silica substrate from a slurry, then drying. In an alternative preferred procedure for the preparation of a supported catalyst system, the metallocene complex is applied to a suitable carrier, for example a dried silica slurried in an appropriate solvent such as, for example, toluene, then treated with MAO or other aluminoxane compound and metallocene complex. The mixture together with the slurried substrate may then be precipitated using a miscible nonsolvent such as dodecane, thereby depositing the catalyst components on the carrier. The catalyst will then be filtered and dried. Alternatively, the mixture may be evaporated to dryness.
The molar ratio of Al from the aluminoxane compound to Zr or other metal from the metallocene complex is from 50:1 to 2000:1, preferably from 100:1 to 1000:1, more preferably from 200:1 to 600:1. The amount of impregnating solution is chosen so that the carrier impregnated with the solution of metallocene complex and aluminoxane compound contains from 5 to 50 micro-mol of metallocene per gram after drying.
The active metallocene catalyst will be temporarily and reversibly passivated for use in the practice of this invention by contacting with an effective amount of a passivating compound to provide a latent metallocene catalyst. Compounds suitable for use as passivating compounds in the practice of this invention are unsaturated hydrocarbons selected from the group consisting of C4-C14 alkynes such as, for example, 1-hexyne, 3-hexyne, and the like, C4-C14 allenes such as 3-methyl-1,2-butadiene and the like, and polycyclic alkenes having an unreactive beta hydrogen, typically containing up to 20 carbon atoms, such as, for example, norbornylene, tetracyclo[4.4.0.12,5.17,10]-3-dodecene and the like.
The metallocene catalyst may be contacted with the passivator in any convenient manner, for example, by suspending the catalyst in a suitable liquid medium containing the passivator. The amount of passivator will generally be sufficient to provide from about 1 to about 5 equivalents of passivator per equivalent of metal in the catalyst complex. The temperature used in conducting the passivation will not be particularly critical, and the process thus may be conducted at any convenient temperature for a period of time sufficient to ensure complete reaction. Generally, temperatures at or below room temperature will suffice, although the passivation will proceed to completion more rapidly when conducted at an elevated temperature, as great as 50 to 100xc2x0 C. or greater, and preferably at a temperature below the volatilization temperatures of the passivator and medium selected. The passivated or latent metallocene catalyst may then be collected by filtration and dried, or used directly without being isolated.
The latent metallocene catalyst, after being dispersed in the reactor, will be reactivated and combined with olefin monomer to carry out the polymerization. Ideally, latent catalyst placed in contact with olefin monomer will become thermally reactivated upon reaching polymerization temperature or shortly thereafter, and will not require an added activator component. However, depending on the particular combination of passivator and catalyst, thermal reactivation may occur very slowly under such conditions. Achieving acceptable levels of catalyst activity within a useful and practical time period may require adding an activator capable of reacting with the latent catalyst to displace and thereby remove the locking group. The activating agent will be selected in view of the particular passivating agent employed. Hydrogen, metal alkyls such as trialkylaluminum and the like are among the compounds that may be found suitable for this use.
While it is not intended that the invention be limited by a particular theory of operation, it appears that deactivation occurs by insertion of unsaturated hydrocarbon passivator into the metallocene complex to form a passivator-metallocene complex containing a bulky group that blocks or markedly retards the subsequent insertion of olefin monomer, which is necessary for olefin polymerization to take place. For example, treating a metallocene complex with norbornylene appears to form a norbornyl-metallocene complex that in turn inserts olefin monomer such as propylene at a very slow rate under the process conditions. Thus, little or no propylene polymerization will be observed. However, as propylene monomer becomes inserted into the complex the blocking group is displaced from the active site, forming an active polymerization catalyst species. The rate that the catalyst becomes reactivated will be influenced by several factors including monomer concentration and reaction temperature. Where the rate that this auto-reactivation process occurs is impracticably slow, an activator, for example, a compound capable of reducing or alkylating the blocking group such as, for example, hydrogen, an aluminum alkyl or the like, may be employed to remove the blocking group and regenerate the active metallocene catalyst complex. Hydrogen appears to be particularly effective in this regard, removing the blocking group by hydrogenolysis and forming an inert hydrocarbon species as a by product.
The amount of activator employed will depend in part upon the particular hydrocarbon component employed in passivating the metallocene catalyst and on the rate that thermal activation will take place in the reactor, as well as on the specific activator selected. The amount of activator will thus be selected to be an amount effective to provide an active polymerization catalyst for the monomers under the polymerization conditions employed in the process. Generally, where an added activator is employed the amount of activator that will be effective in this regard will lie in the range of from about 0.1 to about 100 equivalents, preferably from about 0.1 to about 10 equivalents per equivalent of unsaturated hydrocarbon moiety contained in the latent catalyst.
The latent catalyst compositions of this invention are useful in the polymerization of olefins, preferably alpha-olefins, to form polyolefins using any of the variety of polymerization processes known in the art for the production of polyolefins including in suspension, in solution in an inert liquid hydrocarbon, in bulk i.e. liquid monomer, and in stirred or fluidized bed gas phase polymerization processes and the like. As used herein, a xe2x80x9cpolyolefinxe2x80x9d is meant to include homopolymers, copolymers, and terpolymers of such olefins and may optionally contain dienes, aromatic compounds with vinyl unsaturation and/or carbon monoxide.
Generally, olefin monomers suitable for these purposes will have from 2 to 14 carbon atoms and typically include, but are not limited to, ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, styrene, substituted styrene and the like. Dienes that may optionally be polymerized with the olefins are those which are non-conjugated, and may be straight chain, branched chain or cyclic hydrocarbon dienes having from about 5 to about 15 carbon atoms. Examples of suitable straight chain, non-conjugated acyclic dienes include 1,4-hexadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene and 1,6-octadiene; branched chain acyclic dienes such as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene and mixed isomers of dihydromyricene and dihydrocinene. Single ring alicyclic dienes such as 1,3-cyclopentadiene, 1,4-cyclohexadiene, 1,5-cycloctadiene and 1,5-cyclododecadiene and multi-ring alicyclic fused and bridged ring dienes such as tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene, bicyclo-(2,2,1)-hepta-2,5-diene, alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-methylene-2-norbornene, 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and norbornadiene may also be found suitable.
Irrespective of the polymerization process employed, polymerization or copolymerization should be carried out at temperatures sufficiently high to ensure reasonable polymerization rates and avoid unduly long reactor residence times. Generally, temperatures range from about 0xc2x0 to about 120xc2x0 C. with a range of from about 20xc2x0 C. to about 95xc2x0 C. being preferred from the standpoint of attaining good catalyst performance and high production rates. More preferably, polymerization according to this invention is carried out at temperatures ranging from about 50xc2x0 C. to about 80xc2x0 C.
Olefin polymerization or copolymerization according to this invention may be carried out at monomer pressures of about atmospheric or above. Generally, monomer pressures range from about 20 to about 600 psi, although in vapor phase polymerizations the monomer pressures should not be below the vapor pressure at the polymerization temperature of the olefin to be polymerized or copolymerized.
The polymerization time will generally range from about xc2xd to several hours in batch processes with corresponding average residence times in continuous processes. Polymerization times ranging from about 1 to about 4 hours are typical in autoclave-type reactions. In slurry processes, the polymerization time can be regulated as desired. Polymerization times ranging from about xc2xd to several hours are generally sufficient in continuous slurry processes.
Inert hydrocarbon diluents suitable for use in slurry polymerization processes include alkanes and cycloalkanes such as pentane, hexane, heptane, n-octane, isooctane, cyclohexane, and methylcyclohexane; aromatics and alkylaromatics such as benzene, toluene, xylene, ethylbenzene, ethyl toluene and the like. It is often desirable to purify the polymerization medium prior to use, such as by distillation, percolation through molecular sieves, contacting with a scavenger compound such as an alkylaluminum compound capable of removing trace impurities, or by other suitable means.
Typical gas phase olefin polymerization reactor systems comprise at least one reactor vessel to which olefin monomer and catalyst components can be added and which contain an agitated bed of forming polymer particles. Typically, catalyst components are added together or separately through one or more valve-controlled ports in the single or first reactor vessel. Olefin monomer is typically provided to the reactor through a recycle gas system in which unreacted monomer removed as off-gas and fresh feed monomer are mixed and injected into the reactor vessel.
Irrespective of the particular process employed, polymerizations with the reactivated metallocene catalyst systems according to the invention will be carried out under conditions that exclude oxygen, water, and other materials that may act as catalyst poisons. Additives to control polymer or copolymer molecular weight such as, for example, hydrogen, may be employed in a manner well known to persons of skill in the art. Although not usually required, those skilled in the polymerization process art will understand that a suitable catalyst deactivator may be added upon completion to terminate polymerization.
Products produced in accordance with the process of this invention are normally solid polyolefins. Homopolymer or copolymer yields are sufficiently high relative to the amount of catalyst employed so that useful products can be obtained without separation of catalyst residues. The polymeric products produced in the presence of the invented catalyst may be fabricated into a variety of useful articles including moldings, fiber and film by extrusion, injection molding, and other methods well known in the art and commonly employed for compounding and fabricating such plastics.
The invention will be better understood by way of consideration of the following illustrative examples and comparison examples, which are provided by way of illustration and not in limitation thereof. In the examples, all parts and percentages are by weight unless otherwise specified.